Rail producing method and producing equipment

ABSTRACT

The present invention provides a method and equipment for producing a rail, the method and equipment being capable of lowering a bend at an end of a rail effectively and the truncation amount thereof. The present invention is a method for producing a rail, characterized by: cooling a hot-rolled mother rail to an ordinary temperature substantially while the length thereof after the hot rolling is maintained; and thereafter cutting the mother rail simultaneously in a predetermined length with at least three cold-sawing machines. Further, the present invention is equipment for producing a rail, characterized by equipped with: a transfer bed capable of moving a mother rail cooled to an ordinary temperature substantially while the length thereof after hot rolling is maintained in the rolling direction and/or in the direction perpendicular to the rolling direction; and at least three cold-sawing machines disposed in parallel with each other on said transfer bed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of PCT Application No.PCT/JP02/05308 which was filed on May 30, 2002 (the “InternationalApplication”). This application claims priority from the InternationalApplication pursuant to 35 U.S.C. § 365. The present application alsoclaims priority under 35 U.S.C. § 119 from Japanese Patent ApplicationNo. 2001-161676 which was filed on May 30,2001. The entire disclosuresof these applications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method and equipment for producing arail and, in particular, to a method and equipment capable of producinga rail with great efficiency and suppressing the generation of a bend atan end of the rail.

BACKGROUND ART

A generally employed method for producing a rail includes the processesof: heating a bloom and hot-rolling it into a predetermined shape; thencutting the hot-rolled material in lengths close to the final productlengths with a hot-sawing machine; thereafter applying or omitting aheat treatment depending on the required mechanical properties; coolingthe cut materials to an ordinary temperature; applying or omitting astraightening treatment depending on the requirement; and subjecting theproduced materials to predetermined inspections such as a flawdetection, a shape inspection and the like.

Rails are laid generally after connecting several rails with each otherby welding in order to protect the ends of the rails from wear caused bythe passages of trains. In such a case, as the wear increases when thewelding planes deviate from each other even slightly, it is strictlyrequired to minimize the deviation created when the end planes of railsare connected face to face. For example, JIS E1101 prescribes that thetolerance of a bend at an end of a 50 kgN rail, an ordinary rail, mustbe 1.0 mm or less in the rightward, leftward and upward directions and0.3 mm or less in the downward direction, per 1.5 m in length. Further,a rail for a high-speed railway or a heavy-load railway, the demands forwhich have been increasing in recent years, is required to have a yetsmaller bend at an end thereof. Furthermore, though the technologies ofproducing an ultra-long rail 500 feet or more in length at a stroke froma continuous casting process to a final process have been disclosedrecently in U.S. Pat. Nos. 5,018,666 and 5,419,387, those technologiesare seldom put to practical use in actual production.

However, when a rail is produced through a continuous process, an en ofthe rail is a portion to which rolling or straightening can hardly beapplied. In a rolling process, it is difficult to achieve a requireddimensional accuracy at a portion within the range from he tip or tailend of a rail to a position a certain length distant from either ofthem. In addition, when a straightening treatment is required and thus astraightener wherein a plurality of rolls are arranged in a zigzagpattern is used, the range from an end to a posit n about 1 to 2 mdistant from the end, namely the range in the length corresponding totwice the interval between two adjacent rolls, is not leveled, namelybecomes a dead zone, and therefore he effect of the straightening cannotbe expected.

A practice commonly employed in order to satisfy the aforementionedcriterion of a bend at an end of a rail in such a situation is to cutoff a portion with a considerable length at an end of the rail and, whenthe criterion is not still satisfied even by doing so, to straighten therail with a press. However, the longer the cut-off length, the higherthe cost and the lower the yield. Further, as the cut-off process of arail or the pressing process thereof requires time for the operation,each of the processes causes a bottleneck when it is incorporated into acontinuous process. On the other hand, when each of the processes isemployed as an off-line process, the productivity deteriorates. Inparticular, when a cold-sawing machine is employed and a cut-off iscarried out at a high speed, a large amount of heat is generated, theheat affects only the cut-off end and, thus, the hardness or the like ofthe end changes largely, and it is therefore necessary either toregulate the cutting speed or to use a special device which does notgenerate a great amount of heat.

Furthermore, the problem here is that straightening by a press canhardly satisfy a precise dimensional accuracy and thus cannot cope withany future stringent criterion.

DISCLOSURE OF THE INVENTION

The present invention is accomplished to solve the problems of theabove-mentioned prior arts, and provides a method and equipment forproducing a rail, the method and equipment being capable ofincorporating a series of processes up to the final process of a productinto a single continuous line and improving the productivity and yield.

The gist of the present invention, which solves the above problems, isas follows.

(1) A method for producing a rail, characterized by: cooling ahot-rolled mother rail to an ordinary temperature substantially whilethe length thereof after the hot rolling is maintained; and thereaftercutting the mother rail simultaneously in a predetermined length with atleast three cold-sawing machines.

(2) A method for producing a rail according to item (1), characterizedby subjecting a hot-rolled mother rail to a heat treatment wherein atleast the head of the mother rail is acceleratedly cooled, from atemperature in the austenite range or higher, at a cooling rate of 1 to10° C./sec.

(3) A method for producing a rail according to item (1) or (2),characterized in that the length of the mother rail after hot rolling isin the range from 100 to 200 m.

(4) A method for producing a rail according to any one of items (1) to(3), characterized by applying or omitting a straightening treatment andsuccessively applying inspection to a mother rail prior to the cut-offwith cold-sawing machines.

(5) A method for producing a rail according to item (4), characterizedby cutting a mother rail with cold-sawing machines at the portions wherea straightening treatment is applied.

(6) A method for producing a rail according to any one of items (1) to(5), characterized by: cutting some portions of a mother rail with alength after hot rolling in the lengths of final products with at leastthree cold-sawing machines; and then cutting the remaining portions inthe lengths of final products with at least two cold-sawing machinesdisposed at the rear side.

(7) Equipment for producing a rail, characterized by being equippedwith: a transfer bed capable of moving a mother rail cooled to anordinary temperature substantially while the length thereof after hotrolling is maintained in the rolling direction and/or in the directionperpendicular to the rolling direction; and at least three cold-sawingmachines disposed in parallel with each other on said transfer bed.

(8) Equipment for producing a rail according to item (7), characterizedin that at least one unit of said cold-sawing machines is fixed and theother units are placed so as to be movable along said transfer bed.

(9) Equipment for producing a rail according to item (7) or (8),characterized by consecutively disposing a cooling bed on which a motherrail is cooled to an ordinary temperature after hot rolling or heattreatment, straightner, inspection apparatuses, said transfer bed, andsaid cold-sawing machines.

(10) Equipment for producing a rail according to any one of items (7) to(9), characterized by disposing additionally two or more units ofcold-sawing machines in parallel with each other at the rear side ofsaid cold-sawing machines on said transfer bed.

(11) Equipment for producing a rail according to any one of the items(7) to (10), characterized in that the number of cold-sawing machines isnot less than the number obtained by adding one to the number of thefinal products that are cut out from a mother rail after hot rolling.

(12) Equipment for producing a rail according to any one of the items(7) to (11), characterized by disposing additionally at least onepunching machine in the vicinity of at least one cold-sawing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing an embodiment of equipment forproducing a rail according to the present invention.

FIG. 2 is an illustration showing another embodiment of cold-sawingmachines according to the present invention.

FIG. 3 is an illustration showing yet another embodiment of cold-sawingmachines according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is hereunder explained in detail based on theembodiments shown in the drawings.

FIG. 1 shows an example of a layout of equipment for producing a railaccording to the present invention. A bloom containing predeterminedcomponents is heated to about 1,300° C. in a reheating furnace 1 andthereafter formed into a mother rail having the sectional shape thereofby passing through a plurality of reversing hot-rolling mills or atandem hot-rolling mill 2. In the present invention, the formed motherrail is successively cooled to an ordinary temperature on a cooling bed5 while the length thereof after the hot rolling is maintained.

Further, in advance of directly cooling a mother rail to an ordinarytemperature on the cooling bed 5, when a heat treatment is required inorder to improve the wear resistance or toughness of at least therailhead, the heat treatment is applied beforehand to the mother railusing a heat treatment apparatus 4 disposed at the downstream side ofthe rolling mill assembly 2. In the heat treatment, a mother rail iscooled after hot rolling from a temperature in the austenite range orhigher at a cooling rate of 1 to 10° C./sec. by a known method. When acooling commencement temperature is low, a mother rail may be heated inadvance of the cooling. As the cooling method, a method of blowing a gassuch as air or a mist is preferable from the viewpoint of keeping thecooling rate proper.

Here, a non-rolled portion or a large bend is apt to be created, at oneor both ends of a mother rail, immediately after hot rolling and may bean obstacle to the subsequent transfer or straightening operation. Insuch a case, a portion with a certain length at an end of the motherrail immediately after hot rolling may be cut off using a hot-sawingmachine 3 disposed between the rolling mill assembly 2 and the heattreatment apparatus 4. The length of a mother rail after hot rolling isdetermined based on production capacity and the equipment specification.However, for the purpose of suppressing the quality difference resultingfrom the temperature difference between the tip and the tail end of amother rail, it is preferable to regulate the length of the mother railin the range from 100 to 200 m and to add a certain length of cuttingallowance thereto.

The cooling bed 5 has a space wherein a long rail may be placed as itis. A mother rail after hot rolling and being cooled to an ordinarytemperature on the cooling bed is: straightened with a straightnerassembly 6 composed of two units, one in the vertical direction and theother in the horizontal direction, if it is required to do so dependingon the extent of a bend or a residual stress; thereafter inspected forquality such as flaws and dimensions with inspection apparatuses 7; andfinally cut in the predetermined length for delivery (of final products)with cold-sawing machines 8 on a transfer bed 9. Those facilities,namely the cooling bed, the straightner assembly, the inspectionapparatuses, the transfer bed and the cold-sawing machines, are arrangedin sequence and constitute a single line. Note that, if a bend or thelike of a mother rail cooled to an ordinary temperature is within atolerance, the rail is not necessarily straightened. The most importantfeatures of the present invention are: to cut a mother rail at pluralportions simultaneously at one time by disposing a plurality ofcold-sawing machines in parallel with each other on a transfer bed whenthe mother rail is cut; and moreover, if a mother rail has beensubjected to a straightner assembly, to cut the mother rail with thecold-sawing machines at the portions that have been straightened. Sincea non-straightened portion at an end of a cut-out product rail iscompletely removed by cutting the mother rail at the portions that havebeen straightened, a product rail that hardly has any bend at an end canbe obtained, as in the case of cutting a mother rail at a centerportion.

The cold-sawing machines 8 are configured so that at least three unitsthereof may be in cutting operation simultaneously. It is desirable toinstall the cold-sawing machines of the number not less than the numberobtained by adding one to the number of the final products that are cutout from a mother rail with a length after hot rolling, that is, thecold-sawing machines of the number that allows a mother rail to be cutoff at both ends and the intermediate portions at one time. For example,when eight product rails 25 m in length each, which are generally used,are cut out from a mother rail with a length after hot rolling of 200 m,it is desirable to install nine cold-sawing machines.

The cold-sawing machines 8 are installed in parallel on the transfer bed9 so that each interval between adjacent two machines may be the same asthe length of each product rail. When the lengths of product rails arealways constant, all cold-sawing machines may be fixed and mother railsmay be cut off while the mother rails are fed in regular succession. Onthe other hand, when the ordered lengths of product rails are not alwaysconstant, it is preferable to fix one unit which acts as the pivot ormore, for example, a unit at an end or units at both ends, of thecold-sawing machines and to install the other units so as to be movablefreely in the longitudinal direction of the mother rail in accordancewith desired lengths.

Further, there is a case where a hole is pierced in the web at an endportion of a product rail for the purpose of connection. In this case,the operation efficiency can be improved further by incorporating apunching machine into a cold-sawing machine and piercing a holesimultaneously with cutting.

A product rail cut into a product length is moved further toward therolling direction or the direction perpendicular to the rollingdirection by the transfer bed 9, is piled in a product stockyard or isloaded directly on a transportation means according to circumstances,and then is delivered.

Here, though FIG. 1 shows an example of a configuration wherein allcold-sawing machines are arranged in a row, as shown in FIG. 2 or 3, aconfiguration may be adopted, wherein the cold-sawing machines areinstalled in the form of two stages so that some portions of a motherrail with a length after hot rolling are cut in the lengths of finalproducts at the front stage and the remaining portions are cut in thelengths of final products with at least two cold-sawing machinesdisposed at the rear stage. This kind of a configuration makes itpossible to shorten and optimize the cutting operation, for example, insuch a case as to cut out a mother rail in a length shorter than usual.In addition, the configuration is effective as an equipment layout whena space is not sufficiently secured for a one-stage configuration.

By using above-mentioned equipment for producing a rail, it becomespossible to make a bend at a rail end very small even with the totallength of truncated portions not increased. That is, even though, by aconventional method of employing a hot-sawing machine, bends have beencreated at the successive heat treatment and cooling and some of thebends have remained at the ends, by the method of the present invention,the straightness of a mother rail is secured comparatively easily at thecenter portion thereof through the rolling and subsequent straighteningand therefore it becomes possible to make a bend at an end very small bycutting the mother rail at the center portion after cooling.Furthermore, an additional truncation of the cut portion is not requiredand a straightening by a press or the like is also not required.

Here, though each of the product rails obtained from both the ends of amother rail with a length after hot rolling still has a large bend atone end of the product rail, the bend can be prevented from remaining byremoving only the end portion sufficiently. Even though such truncationis applied, the truncation is limited to the two portions at both theends of the mother rail with a length after hot rolling and thereforethe number of the truncated portions is one of the several parts ofthose in the case of a prior art. For that reason, even when thetruncated length is sufficiently long, the influence of the yield dropon the cost is suppressed to a low level.

EXAMPLE

As an example of the present invention, six product rails 25 m in lengtheach were produced through the processes of: subjecting a mother rail153 m in length produced beforehand by heating, rolling and thenremoving non-rolled portions to an accelerated-cooling from atemperature in the austenite range or higher to about 500° C. at acooling rate of 2° C./sec.; successively naturally cooling the motherrail to an ordinary temperature; thereafter subjecting it to straightnerand inspection apparatuses; and finally cutting and removing both theend portions in the length of 1.5 m each and, at the same time, cuttingthe other portion in the length of the products using seven units ofcold-sawing machines.

In addition, as a comparative example, six product rails 25 m in lengtheach were produced through the processes of: cutting a mother rail 153 min length produced beforehand by heating, rolling and then removingnon-rolled portions into six pieces of rails 25.5 m in length each usinga hot-sawing machine; successively subjecting them to anaccelerated-cooling from a temperature in the austenite range or higherto about 500° C. at a cooling rate of 2° C./sec. as in the case of theexample of the present invention; successively naturally cooling therails to an ordinary temperature; thereafter subjecting them tostraightners and inspection apparatuses; and finally cutting andremoving both the end portions of each of the rails in the length of0.25 m each.

30 pieces of the product rails were produced as the example of thepresent invention and the same pieces of product rails as thecomparative example by the aforementioned methods, and the bends at theends of each product rail in the vertical direction and the horizontaldirection were measured. The averages of the absolute values of thebends are shown in Table 1. Here, in the examples, as the inventedexample and the comparative-example were identical in the total cut-offlength, whereas the bends were not sufficiently removed in case of thecomparative example, the bends could be suppressed to about one fifth ofthose of the comparative example in case of the invented example. Here,it is a matter of course that, in order to decrease the amount of a bendin case of the comparative example to the same extent as the case of theinvented example, it is necessary to increase the amount of thetruncation.

TABLE 1 Bend in Bend in perpendicular horizontal direction directionInvented example 0.2 mm 0.2 mm Comparative example 1.0 mm 0.9 mm

INDUSTRIAL APPLICABILITY

As it has been explained above, by employing a method and equipment forproducing a rail according to the present invention, it becomes possibleto greatly decrease a bend at an end of the rail and to eliminate anoff-line leveling work. Further, it becomes possible to decrease thetruncation amount and thus to reduce the cost significantly.

All cited references and specification are hereby incorporated herein byreference in their entireties.

1. An equipment for producing at least one particular rail, comprising:a reheating furnace, a hot-rolling mill, a hot sawing machine, aheat-treatment apparatus, a cooling bed, a straightener assembly, aninspection apparatus, an a transfer bed wherein; the transfer bed isconfigured to move a mother rail that is cooled to a particulartemperature while maintaining a length of the cooled mother rail in atleast on rolling direction of the mother rail and at least one directionthat is perpendicular to the rolling direction, wherein at least threecold-sawing machines are disposed parallel to each other at a rear sideof at least one other cold-sawing machines on the transfer bed, forcutting a first portion of the mother rail to a first length, wherein atleast one unit of the cold-sawing machines is fixed a other units of thecold-sawing machines are placed to be movable along the transfer bed forcutting a second portion of the mother rail to a second length.
 2. Theequipment according to claim 1, wherein: the mother rail is cooled onthe cooling bed; the straightener is disposed immediately after thecooling bed; the inspection apparatus is disposed immediately after thestraightener, the transfer bed is disposed immediately after theinspection apparatus; and at least one cold-sawing machine disposedimmediately after the transfer bed.
 3. The equipment according to claim1, wherein a umber of the cold-sawing machines is at least a numberobtained by adding one to a number of the at least one particular railcut from the mother rail after hot rolling.
 4. The equipment accordingto claim 1, further comprising at least one punching machine provided ina vicinity of at least one of the cold-sawing machines.
 5. The equipmentaccording to claim 1, wherein the particular temperature is atemperature of the mother rail to which the mother rail is cooled afterbeing hot-rolled.